AbstractsChemistry

The infrared absorption spectra in the out-of-plane bending (v₂) region of potassium nitrate were studied for three phases. Several types of sampled were used: nujol mulls, fused samples, and N¹⁴-N¹⁵ isotopic mixtures. The existence of three of the reported polymorphic phases was confirmed by the spectra. The transitions between phase II and phase I and between phase III and phase II were followed spectroscopically. The effects of dipole-dipole interactions between nearest neighbors were observed. The out-of-plane bending mode (v₂) and the antisymmetric stretching mode (v₃) were studied for nitrate ion in various alkali halide lattices. The two expected effects were observed. These effects were the narrowing of bands due to complete absence of coupling, and a lowering of absorption frequencies when the lattice constant of the host matrix was increased.